Referring to FIG. 1, a conventional light guide film 1 is adapted for use with a light source 2 for guiding light emitted therefrom. When the light emitted from the light source 2 enters the conventional light guide film 1, it will propagate within the conventional light guide film 1 by total internal reflection. However, since the conventional light guide film 1 is relatively thin comparing to the size of the light source 2, part of the light emitted from the light source 2 will not enter the conventional light guide film 1 and result in energy loss.